<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    div {
      width: 300px;
      height: 300px;
      /* border-width: 5px;
      border-style: solid;
      border-color: aqua; */
      /* 边框的复合写法  简写： */
      border: 5px solid aqua;
      /* 上边框 */
      border-top: 5px solid pink;
      /* 下边框 */
      border-bottom: 10px dashed purple;
    }
  </style>
</head>

<body>
  <div></div>
</body>

</html>